The present invention relates to steering a four-wheeled hospital stretcher, carriage, bed, or cart, by directly connecting one pair of fore and one aft casters together by means of a chain, such that controlled and simultaneous swivelling is achieved. Such mechanism also is suitable for certain other types of mobile carriages.
A wheeled hospital stretcher used for transporting patients is often difficult to control during straight line movement, maneuvering around obstacles, or when negotiating turns. Several devices currently exist which are designed to help the operator steer a stretcher. One example is the standard locking caster which will not swivel when locked and thereby prevents the wheeled stretcher from veering from its directed line of motion. Turning is achieved by essentially turning the stretcher about the fixed wheel. For sideways motion, the locking wheel is disengaged.
Another example of a steering device is the Stryker Fifth Wheel device, comprising U.S. Pat. No. 3,304,116, issued Feb. 14, 1967, which incorporates a fifth wheel operable about a fixed axis approximately centered in the wheeled base frame and can be raised from or lowered to the floor. When lowered, it is forced against the floor and fixed to roll in a straight line and not swivel. The non-swivelling fifth wheel thereby maintains straight line movement of the other four wheels. During turns, the wheels are forced to rotate about the contact point of the fifth wheel. This in essence permits the stretcher to be rotated about its center and provides for a tighter turning radius.
The connection of casters on heavy duty trucks of the factory type by chains for controlling the swivelling of the same in cooperation with a forward swivelled caster which is guided by a pull tongue is old, as shown in U.S. Pat. No. 2,388,692, to House, dated Nov. 13, 1945, and includes an extensive and elaborate system of chains and intermediate sprockets, thereby being expensive to produce.
The provision of four-wheeled vehicles of different kinds in which the front and rear axles turn in opposite directions or the front and rear pairs of wheels respectively turn in opposite directions to effect sharp turns in directions of movement is old in U.S. Pat. Nos. 2,330,557, to Collis, dated Sept. 28, 1943; 3,398,971, to Seidel, dated Aug. 27, 1968, and 3,734,538, to Humes, dated May 22, 1973.